The present invention relates to a marrow nail for the treatment of bone fractures according to a marrow cavity nailing procedure.
Marrow nailing methods are known, for example, the publication entitled "Die Bundel-Nagelung" [Bundle Nailing] published by Springer-Verlag, Berlin, Gottingen, Heidelberg, 1961, pages 3-26 and 56-58, discloses the treatment of fractures in long tubular bones by a marrow nailing method in which a metallic marrow nail is driven through the marrow cavity of a selected bone across the location of the fracture, and is there anchored in the marrow cavity to stabilize the fracture after the bone has been appropriately repositioned. After complete healing of the fracture, the marrow nail is then removed. The desired stabilization of a fracture in such a marrow nailing procedure is realized by clamping the marrow nail in either the transverse or longitudinal direction, with the marrow nail having a variety of permissible cross-sectional configurations.
However, the known metal marrow nails have several drawbacks. The rigid metal nails used in the prior art involve the risk of splitting the bone, the risk of the nail tip being caught at an inappropriate location, the risk of the nail being bent, the risk of bending the nail during the nailing process due to the relatively weak resistance of the nails to bending stresses. Other types of marrow nailing, such as, for example, bundle nailing by means of a bundle of thin elastic steel nails, have the drawback that their stability is not always ensured and that certain treatments are necessarily employed in conjunction with each type of nail.
For the treatment of pertrochanteric and subtrochanteric fractures according to the marrow nailing procedure, it is also known to use so-called spring nails which are arranged in the marrow tube in an elastically clamped arrangement and are distributed in a fan shape at the end opposite the point where they are driven in. If there is pressure stress on a bone stabilized in this manner, such pressure is distributed to the bone uniformly over the entire length of the nails. The prior art spring nails provide good support in the proximal part of the fracture as well as good rotational stability. Due to the resiliency of these prior art spring nails, it is possible to employ turning of a preliminary driver to cause threading of the bone fragments and accurate repositioning of the fragments. As with the use of rigid marrow nails, spring nails must be made of a high quality metal to produce the required strength and elasticity characteristics and to avoid adversely affecting the bone tissue. Additionally, if spring nails are employed, it is the custom to employ three or more nails to fix pertrochanteric fractures.
The prior art bone nails have the drawback that they are bodies made of a foreign material with respect to the human body, so that it is necessary in every case to extract the prior art bone nails in a second surgical procedure. Moreover, since the characteristics of the prior art bone nails are not well adapted to conform to those of the surrounding bone material, relative movements between the bone material and the bone nails cause damaging results due to their different stress behavior when the bone is placed under load.